Mobile Communication application for V2V Systems Marius Vochin1, Hayder AL-Amily2 Telecommunications Department, Faculty of Electronics, Telecommunications and Information Technology, University POLITEHNICA of Bucharest - UPB, Bucharest, Romania
[email protected] 2 Electronics Department, Faculty of Electronics, Telecommunications and Information Technology, University POLITEHNICA of Bucharest - UPB, Bucharest, Romania
[email protected] 1
Abstract — The increasing number of personal and commercial vehicles in transit induces a high volume of road traffic, which can often lead to serious incidents such as permanent traffic jams, increased gas pollution, accidents with material or even human losses. Technology and transportation infrastructure providers are required to provide safer, more scalable, flexible, and cost effective solutions to these problems. Intelligent Transportation Systems (ITS) have been developed to meet these requests, by offering traffic monitoring, guidance or alerting communication capabilities to or between vehicles, or intelligent infrastructure safety elements. This paper investigates the possibility of using common hardware such as a smart phone to achieve V2V or V2I communication, as a solution to implement offline alerting capabilities in Intelligent System for Vehicle Navigation Assistance (SIAN) research project.
I.
INTRODUCTION
Modern ITS should offer various solutions for traffic management and optimization, by integrating different cooperating technologies, for monitoring, alerting and directing cars. Current research has identified two common technologies to be used as communication network for ITS: the MANETs (Mobile Ad Hoc Networks) [1] which are wireless selfreconfigurable networks, and more specifically VANETs (Vehicular Ad Hoc Networks) [2], in which the nodes are represented by vehicles. Intelligent navigation systems have been developed to assist drivers with driving directions and could offer traffic information, routing capabilities and even alerts about potentially hazardous conditions [3]. Alerts are usually provided by infrastructure safety systems, or can even be collected from users of social navigation systems such as Waze. SIAN is an innovative research project which aims to improve navigation process by monitoring internal car sensors through an onboard diagnosis interface (OBD), present in each recent vehicle [4]. Relevant OBD traffic information could be presence of ice or rain detected by sensors, car malfunction (MIL) or engaging of active security systems such as Anti-lock braking system (ABS), Emergency brake assist (EBA), Electronic stability control (ESC) due to hazardous conditions. Once an alert
detected, short range communication technologies such as vehicle to vehicle (V2V), vehicle to infrastructure (V2I) or vehicle to everything (V2X) could be used to warn neighboring vehicles. Also, an alert could be posted on the online navigation server in use, and even a call to emergency services (112) could be automatically initiated if no driver interaction is received and a major event such as airbag engaging is detected. Research challenges in the field of intelligent navigation systems and V2X communication technology are especially important as they are seen as components of tomorrow’ autonomous vehicles. One of the most popular V2X communication technology that could emerge in the market in the near future is the Wi-Fi based Dedicated Short Range Communication (DSRC) [5], a two-way short to medium range wireless communication capability that permits very high data transmission, critical in communicationsbased active safety applications. In Report and Order FCC-03324, the Federal Communications Commission (FCC) allocated 75 MHz of spectrum in the 5.9 GHz band to be used by Intelligent Transportations Systems (ITS) vehicle safety and mobility applications [6]. Some disadvantages of this technology are dedicated hardware requirements, and a possible high cost at the beginning, which could delay large scale systems implementations. SIAN proposes a low-cost solution that can use a regular Android based Smartphone, with Bluetooth and Wi-Fi connectivity. Additionally, a standard Bluetooth OBD dongle will be used to acquire car data and V2V alerts will be broadcasted through Wi-Fi Direct (initially named Wi-Fi P2P) wireless communication. By using off the shelf hardware, such a solution could easily be implemented in a short period of time, with small costs. The paper is structured as follows: a brief introduction of vehicular communication and intelligent navigation systems is presented in the first part, and an overview of Wi-Fi Direct technology is presented in the second part. The third part of the paper share some of the preliminary communication application implementation details, the fourth part shows experimental
results of validation tests and the latter shows main paper conclusions. II.
ANDROID P2P WIRELESS COMMUNICATION
Wi-Fi Direct (formerly called Wi-Fi P2P) is a relatively new technology introduced first in Android 4.0 "Ice cream sandwich", and supported by the clear majority of Android devices that are currently in use (97.4% of total devices according to Google [7]). Using this API, devices can be discovered and connections can be initiated with others that support the same technology, with high speed link, without needing of any intermediate equipment like access points (router or Wi-Fi hotspot). Therefore, connections can be direct and faster compared to Infrastructure mode that needs infrastructure access point in the middle. P2P API use these main parts [8]: • • •
WifiP2pmanager that discovers, requests and connects to other peers. Listener to notify if the connection is successful or fails. Intent to notify about some events like connection dropping or new peers discovering.
The Wi-Fi API broadcasts Intent type messages when Wi-Fi P2P event happens, such as discover or WIFI changed. The following listeners will be used in our proof of concept implementation: ActionListener, ChannelListener, ConnectionInfoListener, GroupInfoListener and PeerListListener, together with these types of Intents: • • • •
WIFI_P2P_CONNECTION_CHANGED_ACTIO N WIFI_P2P_PEERS_ACTION WIFI_P2P_STATE_CHANGED_ACTION WIFI_P2P_THIS_DEVICE_CHANGED_ACTION
A broadcast receiver Class makes possible to receive an intent from Android operating system, so the program can respond to events of interest. To create a broadcast receiver, it must be created a class first to extend BroadcastReceiver Class, to be able to send activity status update as well as to get access to the Wi-Fi hardware and communication channel if needed. III.
PRELIMINARY APPLICATION IMPLEMENTATION
To create a P2P application, first it must be checked that the Wi-Fi hardware can be accessed and P2P functions are supported. Also, it must be checked if P2P function flag is switched on or off, and this can be done when the broadcast receiver receives the WIFI_P2P_STATE_CHANGED_ACTION intent. The onCreate method, obtains an instance to wifiP2pManager and registers the application with the Wi-Fi P2P framework by calling initialize method. This allows broadcast receiver to notify the application about events of interest and react accordingly.
A. Peers discovering To discover if any neighboring peer is available (which should be assimilated to another vehicle), the discoverPeers method is called, which functions asynchronously and then determines if the process returns onSuccess() or onFailure() status codes. If the discovery process succeeds and detects peers, the system broadcasts the WIFI_P2P_PEERS_CHANGED_ACTION intent. A list of available peers can also be requested by calling requestPeers method, which is also asynchronous, and checks for peers at any time to see their availability. B. Connecting to peers After finding the appropriate peer from the list, a connection can be initiated to it by using the connect method, which calls WifiP2pConfig to request device info of the peer, and returns the success or fail of the connection. C. Transfer Data Once the two devices connected, sockets can be used to transfer data. This is done by creating socketServer, which waits for connection on a specific port and runs in the background. After that, a socket is created for the client to connect to the predefined specific IP and port address to the server. UDP connection is implemented with Socket() constructor, for a fast and connectionless data transmission: socket.bind(null); socket.connect((new SOCKET_TIMEOUT);
InetSocketAddress(host,
port)),
For our use case, which supposes sharing of port and IP information and then finally sharing data with other devices, we will use the former, since it allows to append a string map with the service. A connection info listener is needed, and connection with the device can be established based on the received information as a part of DnsSdTxtRecordAvailable or DnsSdServiceAvailable callbacks. After the connection has been established, the chosen data can be send or receive between the devices. Application, was built conforming to Google developer description of Wi-Fi P2P [9]. System.currentTimeMillis() method was used to calculate the time in millisecond from 1/1/1970 till present. Since having the same time on both devices was not an easy task (time synchronization would be even a bigger problem with several devices), timestamps were added to determine start of message and completion. Time difference was measured between start and completion moment to calculate the exact message duration time. IV.
EXPERIMENTAL VALIDATION
Two identical Asus FonePad note 6 (K00G, presented in Fig. 1) running Android version 4.4.2 (Code name KitKat) were used for validation test scenarios.
400 Time in ms
Different measurements were performed in lab conditions such as: broadcast alert propagation time at 10 and 15 meters, and larger data messages were transmitted (~ 2MB) to
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Figure 3 Transmission data in (ms) for 10m long and for different sizes.
determine scalability parameters such as CPU, memory and network interface load. Implemented application performance and scalability aspects were measured and the CPU determined usage was very small, as it can be seen in Fig. 2 (brown line), considering the powerful Dual-core 2.0 GHz Intel Atom Z2580 processor provided on the devices.
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Figure 1. Implementation devices used in tests.
The same measurement was performed by relocating the test devices at a 15-meter distance and sending only larger messages sizes, with results being presented below:
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Figure 4 Transmission in (ms) for 2.2 MB data for 15m long.
V. Figure 2. Application CPU usage.
Also, regarding the usage of RAM memory, only a very small amount of the total 2GB available is used by the implemented application, and the peak network rate was of 2Mbps, corresponding with the maximum message size transmitted. The following results were obtained by measuring the transmission time of 3 different message sizes, with the devices located at a 10 meters’ distance. The transmission time is expressed in ns, and each measurement was repeated several times for each message size, with results being presente d in Fig. 3:
CONCLUSIONS
This paper investigated the usage of Android Wi-Fi Direct communication in vehicular applications, as a cost-effective alternative to DSRC communications. This was choosed as a fast going to market alternative, since the Wi-Fi is an old technology (starting from 1997) and it’s available almost everywhere. Also, there are different standards for DSRC in Japan and Europe, which, together with the significant cost end specialized hardware required, could delay even more the large-scale implementation of such communication technology. The preliminary implementation software and hardware resources requirements are low, making this a feasible solution for offline (without requiring an active internet connection on the sender or receiver devices) alert communication to
neighboring vehicles, suitable to be use in the innovative architecture of SIAN research project. This type of communication can also be extended to inform pedestrians if they face emergency situations, and can be used in V2I scenarios as a mean for the traffic infrastructure to signal different traffic information. Future work should address easier device configuration, with statically or automatic address setup, in order to permit faster message transmission. Security concerns should also be addressed and also a vehicle localization procedure could add value and relevance to alerts. ACKNOWLEDGMENT This work has been funded by University Politehnica of Bucharest, through the “Excellence Research Grants” Program, UPB – GEX. Identifier: UPB–EXCELENȚĂ–2016 Research project Intelligent Navigation Assistance System, Contract number 101/26.09.2016 (acronym: SIAN), and partially supported by UEFISCDI Romania under grant no. 60BG/2016 “Intelligent communications system based on integrated infrastructure, with dynamic display and alerting - SICIAD”. REFERENCES 1.
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